江汉平原湖区农田防护林的小气候效应研究

在区域开发中,平原湖区的林业发展潜力很大,同时,湖区农田防护林的建设,也是促进生态平衡的一项重要措施,防护林能进一步改善湖区小气候环境,尤其对保障农业生产有着相当重要的意义。通过对江汉平原湖区的农田防护林网内的小气候效应温度,湿度,风速等要素的观测数据进行研究,我们得出的结果表明：江汉平原湖区农田林网的建设,除提供工农业生产所需的林木外,随着林木的增多,林网的完善,还可调节气候,保持水土,防风固沙     

森林可持续经营基本任务与实现途径

本文以区域可持续发展理论为指导,通过森林可持续经营内涵、目标的分析,提出了用于指导区域森林可持续经营研究与实践的基本思路和途径     

Short-term wind speed forecasting based on random forest model combining ensemble empirical mode decomposition and improved harmony search algorithm

ABSTRACT

Wind speed forecasting plays an important role in power grid dispatching management. This article proposes a short-term wind speed forecasting method based on random forest model combining ensemble empirical modal decomposition and improved harmony search algorithm. First, the initial wind speed data set is decomposed into several ensemble empirical mode functions by EEMD, then feature extraction of each sub-modal IMF is performed using fast Fourier transform to solve the cycle of each sub-modal IMF. Next, combining the high-performance parameter optimization ability of the improved harmony search algorithm, two optimal parameters of random forest model, number of decision trees, and number of split features are determined. Finally, the random forest model is used to forecast the processing results of each submodal IMF. The proposed model is applied to the simulation analysis of historical wind data of Chaoyang District, Liaoning Province from April 27, 2015 to May 22, 2015. To illustrate the suitability and superiority of the EEMD-RF-IHS model, three types of models are used for comparison: single models including ANN, SVM, RF; EMD combination models including EMD-ANN, EMD-SVM, EMD-RF; EEMD combination models including EEMD-ANN, EEMD-SVM, EEMD-RF. The analysis results of evaluation indicators show that the proposed model can effectively forecast short-term wind data with high stability and precision, providing a reference for forecasting application in other industry fields.     

Multicriteria evaluation of simulated logging scenarios in a tropical rain forest

Forest growth models are useful tools for investigating the long-term impacts of logging. In this paper, the results of the rain forest growth model FORMIND were assessed by a multicriteria decision analysis. The main processes covered by FORMIND include tree growth, mortality, regeneration and competition. Tree growth is calculated based on a carbon balance approach. Trees compete for light and space; dying large trees fall down and create gaps in the forest. Sixty-four different logging scenarios for an initially undisturbed forest stand at Deramakot (Malaysia) were simulated. The scenarios differ regarding the logging cycle, logging method, cutting limit and logging intensity. We characterise the impacts with four criteria describing the yield, canopy opening and changes in species composition. Multicriteria decision analysis was used for the first time to evaluate the scenarios and identify the efficient ones. Our results plainly show that reduced-impact logging scenarios are more 'efficient' than the others, since in these scenarios forest damage is minimised without significantly reducing yield. Nevertheless, there is a trade-off between yield and achieving a desired ecological state of logged forest; the ecological state of the logged forests can only be improved by reducing yields and enlarging the logging cycles. Our study also demonstrates that high cutting limits or low logging intensities cannot compensate for the high level of damage caused by conventional logging techniques.     

Air Pollution Effects on Forest Trees in Balikesir,Turkey

Air pollution has become an actual problem in Balikesir because of rapid urbanisation and increasing of the polluting sources. Air pollutionproblems occur under the unfavorable meteorological conditions which increase in frequency of occurrence in winter due to use of low quality lignite coals for heating. The `Protection of Air Quality' in Turkey dated 1986 is based on the human health criteria. But the critical limit values are lethal for the forest trees as far as SO₂ is concerned. The field observations showed that leaves of the trees have yellow spots indicating acid burns in Balikesir. This study aims at determining the relationships between the SO₂ concentrationsin the air under selected climatic conditions, and the effects of air pollution on forest trees in Balikesir. Samples of leaves were collected from the City Parks in Balikesir, Deirmenboaz forested area located 10 km far fromBalikesiron the Balikesir-Bursa highway, and from the forestation areas near the Balikesir-Edremit highway. Sulfur contents of the leaves were very high especially in the city (2650–5300 g m^-3).Samples from other areas had values lower than this range but above the usual values (850–3612 g m^-3). The diameter increments of the trees were found to be lower and these results clearly showed the adverse impacts. Negative correlations were found between these sulfur concentrations and the daily mean temperatures and wind speeds. Positive correlation was seen between these concentrations and pressures, humidities. Emission sources must be controlled in order to safeguard the forests which protects the soil, facilitate water production, assimilate carbon dioxide in air and produce oxygen. It must be considered that the problems are not only regional but have a global identity.     

东涌工业污水处理站污泥处置方法的研究和探讨

本文通过番禺区东涌工业污水处理站污泥特性和污泥堆肥技术的研究,提出了污泥堆肥的可行性,并用之于实践,变废为宝,解决了污泥的处置问题.     

Visual Aesthetic Quality of Northern Ontario's Forested Shorelines

Only a few empirical studies on forest aesthetics have adopted a water-based perspective for observers and have investigated the perceived visual quality of forested shorelines. In forested environments with many lakes, such as the boreal forest in the Canadian Shield, individuals have greater exposure to forests from water-based rather than in-stand vantage points. This study employed the psychophysical research direction to explore the relationships between scenic beauty and biophysical characteristics of the forested shorelines in the boreal forests. Two model forms were tested. One model related the variation of shoreline forest aesthetic evaluations of near-vista views (140 m offshore) to a set of forest mensuration data. Tree size, tree mortality, conifer shrubs, tree density, amount of hardwood, and slope explained 60.2% of the variance in scenic beauty between the study sites. A second model was calibrated to test the relationship between an already existing ecosystem vegetation classification system and the aesthetic evaluations of the same forested shorelines. When the ecosystem classification was simplified to eight groups, the model explained 48.5% of variance. These models suggest that the psychophysical approach to studying aesthetics can be applied successfully to near-vista evaluations of scenic beauty. The finding that a forest ecosystem classification system is highly related to scenic beauty suggests that, at least in the boreal forest, managers can reasonably estimate the scenic beauty of forested shoreline environments from an ecosystem classification, with little need for intensive data on these sites.     

Comparative Influence of Forest Management and Habitat Structural Factors on the Abundances of Hollow-Nesting Bird Species in Subtropical Australian Eucalypt Forest

We examined the impact of single-tree selective logging and fuel reduction burns on the abundance of hollow-nesting bird species at a regional scale in southeastern Queensland, Australia. Data were collected on species abundance and habitat structure of dry sclerophyll production forest at 36 sites with known logging and fire histories. Sixteen bird species were recorded with most being resident, territorial, obligate hollow nesters that used hollows that were either small (<10 cm diameter) or very large (>18 cm diameter). Species densities were typically low, but combinations of two forest management and three habitat structural variables influenced the abundances of eight bird species in different and sometimes conflicting ways. The results suggest that habitat tree management for biodiversity in production forests cannot depend upon habitat structural characteristics alone. Management histories appear to have independent influence (on some bird species) that are distinguishable from their impacts on habitat structure per se. Rather than managing to maximize species abundances to maintain biodiversity, we may be better off managing to avoid extinctions of populations by identifying thresholds of acceptable fluctuations in populations of not only hollow-nesting birds but other forest dependent wildlife relative to scientifically valid forest management and habitat structural surrogates.     

大兴安岭林区地下火形成火环境研究

地下火作为森林中一种难以控制的燃烧现象,其形成机理极为复杂。我国大兴安岭林区是森林地下火的多发地区。对该地区2002年发生的地下火研究表明：丰富的近土壤层和地下可燃物是森林地下火发生的物质条件,气象条件促进了森林地下火的发生,特别是在遇到降水少、长期干旱、地面温度增加、相对湿度降低和可燃物干燥的情况下,就很容易引起地下火灾。地下火有地理和时间分布特征。地表火主要发生在原始森林区域,如针叶林、阔叶林或针阔混交林,都有可能发生地下火。地下火一般燃烧速度慢,持续时间长,燃烧充分,具有隐蔽性强、燃烧不连续、方向易变等特点,地下火在所有火灾中对森林危害最大,特别是对落叶松、樟子松、云杉等的破坏更为严重。     

Lowest Effect Levels of Lead and Mercury on Decomposition of Mor Layer Samples in a Long-Term Experiment

Indications of possible negative effects of lead (Pb) and mercury(Hg) on microbial respiration in Southern Swedish forest humus layers led to experiments on dose-response relationships by additions of metal salts in the laboratory. Respiration rates andweight loss due to decomposition of organic material were measured. For relevance to field situations metal doses were low,the time span was long, 550 days including freeze storage, and microbial activity was kept up by plant litter additions. We looked for effects of Pb and Hg at levels moderately elevated above the Southern Swedish reference, as well as combined effectsof Pb + Hg. A reduction in respiration and decomposition of10% was found at about 225–245 g g^-1 of total Pb, i.e. ata Pb level elevated 3.5 times. Although small effects of Hg werefound even at the lowest dose level, 10% inhibition of microbialactivity appeared temporarily at about 2–3 g g^-1 of total Hg, i. e. at 6–8 times the reference level. There were nolong-term additive effects of Pb and Hg on decomposition. Type of anion had a strong influence on the test, chlorides of Pbbeing more toxic than nitrates. Long-term monitoring and maintenance of microbial activity during the experiment were prerequisites for the occurrence of effects at low metal levels.